Rename "signature" to "metadata"

Bug: 186396424
Test: atest ApexTestCases MicrodroidHostTestCases
Change-Id: Id401d33edc6c6d4aba2b5982c8ab75820faea793
diff --git a/microdroid_manager/Android.bp b/microdroid_manager/Android.bp
index 38d500c..ea811c8 100644
--- a/microdroid_manager/Android.bp
+++ b/microdroid_manager/Android.bp
@@ -12,7 +12,7 @@
         "libandroid_logger",
         "libanyhow",
         "liblog_rust",
-        "libmicrodroid_signature_proto_rust",
+        "libmicrodroid_metadata_proto_rust",
         "libprotobuf",
         "libserde_json",
         "libserde",